Neurophysiology Flashcards
Regarding the neuronal resting membrane potential, which of the following is true?
Select one:
1. Hyperpolarise with moving out of chloride.
2. Depolarise with rapid moving out of sodium.
3. Repolarise with moving out of potassium
4. Repolarise with rapid cellular entry of sodium.
5. Depolarise with rapid cellular entry of potassium.
Repolarise with moving out of potassium
An action potential is initiated in the axon hillock when the synaptic signals received by the dendrites and
soma are sufficient to raise the intracellular potential from -70 mV to the threshold potential of - 55mV.
When this potential is reached, the Na+ channels present in the axon initial segment will open. This Na+
influx causes a rapid reversal of the membrane potential from -90 to +40 mV. When the membrane potential reaches +40mV, the Na+ channels close and the voltage-gated K+ channels open. K+ ions move out of the axon, and ‘repolarizes’ the membrane.
Which one of the following is not a characteristic feature of Kleine-Levin syndrome?
Select one:
1. Episodic nature
2. Hypersomnia
3. Male predominance
4. Hypertension
5. Hyperphagia
Hypertension
Kleine-Levin syndrome affects males predominantly, the sufferers are usually under the age of 25, patient
sleeps for 20 hours or more per day during an episode and it can last for several days. Hypersomnia and
Hyperphagia are the important characteristic features.
Which type of EEG trace is expected when eyes are closed during relaxation?
Select one:
1. Gamma
2. Beta
3. Theta
4. Alpha
5. Delta
Alpha
Alpha waves are predominant when eyes are closed, but the patient is not sleeping.
Which of the following associated with neuroendocrine changes during sleep is correct?
elect one:
1. Testosterone decreases when sleep starts
2. GH decreases when sleeping
3. Cortisol shoots up in slow wave sleep
4. During REM sleep melatonin decreases
5. Prolactin decreases in early morning sleep
During REM sleep melatonin decreases
Melatonin regulates circadian rhythms. It has both synchronizing and phase-shifting properties in the
regulation of biological rhythms. It reduces during REM sleep.
A 34-year-old patient who is taking sulpride undergoes EEG investigation for detecting drug-related EEG
changes. What would you expect to see?
Select one:
1. decrease in delta activity
2. new onset spike and waves
3. decrease in alpha activity
4. slowing of beta activity
5. decrease in theta activity
Slowing of beta activity
Slowing of beta activity with an increase in alpha, theta and delta activity is seen with antipsychotics.
1-2 Hz shaped wave pattern is seen in
Select one:
1. Hepatic encephalopathy
2. Huntington’s disease
3. Alzheimer’s disease
4. CJD
5. Multi-infarct dementia
CJD
The classic EEG finding in CJD is generalized 1-2 Hz bi- or triphasic sharp- and slow-wave complexes.
These may not appear until very late in the clinical course, if at all, and may require repeated testing. The
earliest EEG finding is more often rhythmic generalized slowing.
Which of the following disorders is characterised by a predominant presence of triphasic waves in EEG?
Select one:
1. Head injury
2. Depressive pseudodemntia
3. Herpes simplex encephalitis
4. Dementia of Alzheimer’s type
5. Hepatic encephalopathy
Hepatic encephalopathy
Triphasic waves (1.5 to 3.0 per second high-voltage slow-waves) are a distinctive but nonspecific
electroencephalographic (EEG) pattern originally described in a stuporous patient as ‘blunted spike and
wave.’ Since their findings were limited to patients with hepatic failure, triphasic wave encephalopathy
(TWE) became synonymous with hepatic encephalopathy. Since then, TWE has been associated with a wide range of toxic, metabolic, and structural abnormalities
Which of the following statement concerning REM sleep is INCORRECT?
Select one:
1. EEG shows activity similar to awake state
2. Rapid eye movements are noted
3. Cardiac activity is similar to awake state
4. Muscle tone is similar to awake state
5. Penile erection occurs
Muscle tone is similar to awake state
Criteria for REM sleep includes not only rapid eye movement, but also low muscle tone and an EEG pattern that is for most part similar to awake stage or stage 1 sleep but with intermittent appearance of rapid, low voltage EEG (saw tooth pattern) .
REM rebound on cessation is seen with the use of which of the following?
Select one:
1. Zolpidem
2. Modafinil
3. SSRIs
4. Methylphenidate
5. Inhalants
Methylphenidate
Stimulants reduce the total sleep time by decreasing both REM sleep and Slow Wave Sleep. On cessation
of stimulants (except modafinil), REM rebound occurs.
REM sleep includes which of the following physiological features?
Select one:
1. Abolition of tendon reflexes
2. Increased parasympathetic activity
3. Reduced heart rate
4. Increased recall of dream if awoken
5. Reduced cerebral blood flow
Increased recall of dream if awoken
Features of REM sleep:
1. Increased recall of dream if awoken
2. Increased sympathetic activity
3.Increased heart rate, systolic blood pressure, respiratory rate, cerebral blood flow
4. Penile erection or vaginal blood flow
5. Increased protein synthesis
6. Occasional myoclonic jerks
7. Maximal loss of muscle tone
8. Transient runs of conjugate ocular movements.
Features of non-REM sleep
1. Reduced recall of dreaming if awoken
2. Increased Parasympathetic activity
3. Decreased heart rate, systolic blood pressure, respiratory rate, cerebral blood flow
4. abolition of tendon reflexes
5. An upward ocular deviation with few or no movements.
Which one of the following is characteristic of REM sleep?
Select one:
1. Atonia
2. Reduced recall of dreaming if awoken
3. Decreased heart rate
4. Abolition of tendon reflexes
5. Upward ocular deviation with few or no movements
Atonia
Features of REM sleep include Increased recall of dream if awoken, Increased sympathetic activity,
Increased heart rate, systolic blood pressure, respiratory rate & cerebral blood flow, Penile erection or vaginal blood flow, Increased protein synthesis, Occasional myoclonic jerks, Maximal loss of muscle tone and transient runs of conjugate ocular movements. Nightmares occur in REM sleep - hence they are well recollected
Which of the following is an innovative treatment with some beneficial effect in dystonia?
Select one:
1. Vagal nerve stimulation
2. Transcranial magnetic stimulation (rTMS)
3. Leucotomy
4. Behavioural reversal therapy
5. Nerve ablation
Transcranial magnetic stimulation (rTMS)
Repetitive transcranial magnetic stimulation (rTMS) is being increasingly explored as a therapeutic tool for
depression, schizophrenia and movement disorders associated with deficient inhibition throughout the
central nervous system. There is some evidence for its use in dystonia as well though the evidence is very
preliminary compared to the convincing evidence in the treatment of depression and hallucinations.
The brain region that acts as monitor of circadian rhythm is
Select one:
1. Hippocampus
2. Suprachiasmatic nucleus
3. Locus ceruleus
4. Nucleus accumbens
5. Dorsal medial thalamus
Suprachiasmatic nucleus
The master clock of the brain is the suprachiasmatic nucleus (SCN) located in the anterior hypothalamus -
this orchestrates circadian rhythms and is synchronized by signals from the retina.
Which of the following brain regions when stimulated via magnetic pulse reduces depression?
Select one:
1. Right temporal
2. Left prefrontal
3. Right occipital
4. Left temporal
5. Right parietal
Left prefrontal
Magnetic stimulation may have therapeutic effects in affective disorders similar to ECT. Few studies have
reported a beneficial effect of left prefrontal rTMS in severe depression.
Which one of the following statements is true about normal EEG?
Select one:
1. The normal dominant alpha rhythm is usually achieved by 8-10 years old
2. Closing the eyes usually abolishes the dominant alpha rhythm.
3. Ongoing delta activity when awake is almost always abnormal in the adult
4. Beta activity is almost always abnormal in the adult
5. The dominant alpha rhythm is seen in the Fronto-temporal region.
Ongoing delta activity when awake is almost always abnormal in the adult
The normal dominant alpha rhythm is usually achieved by 12-14 years old. The dominant alpha rhythm is
seen posteriorly in the occipito-parietal region. Opening the eyes, concentrating, arousal states and anxiety usually abolishes the dominant alpha rhythm. Ongoing delta activity is almost always abnormal in the adult
Some Beta activity is seen in most adults, predominantly pre-central. Small amounts of theta activity are normal in adults.
Which of the following is a posterior pituitary hormone?
Select one:
1. Melatonin
2. Gonadotrophin
3. Prolactin
4. Testosterone
5. Oxytocin
Oxytocin
Vasopressin (ADH - antidiuretic hormone) and oxytocin are peptides differing from each other in only two
amino acids in their sequences. Both are synthesized in the supraoptic nuclei and paraventricular nuclei of
the hypothalamus. (posterior pituitary hormones)
An EEG showing high amplitude repetitive bilaterally synchronous symmetrical polyphasic sharp wave and
slow wave complexes, which occur every 4-15 seconds are characteristic of
Select one:
1. Neurosyphilis
2. Creutzfeldt Jacob disease
3. Herpes simplex encephalitis
4. Sub acute sclerosing pan encephalitis
5. Absence seizures
Sub acute sclerosing pan encephalitis
CJD-Periodic stereotyped discharges in the EEG at a rate of about 1 per second Herpes simplex
encephalitis-episodic discharges recurring every 1-3 seconds with variable focal waves over the temporal
areas. Neurosyphilis- non-specific increase in slow waves occurring diffusely over the scalp. Absence
seizures-multiple spike and slow wave complexes, Regular 3 Hz Complexes.
K complexes during sleep EEG are seen during
Select one:
1. Stage 3 sleep
2. Stage 4 sleep
3. Stage 2 sleep
4. Stage 1 sleep
5. REM sleep
Stage 2 sleep
The K-Complex is a phasic transient EEG activity that occurs around once every 2-3 minutes during stage 2
non-REM sleep. In REM sleep, the K-Complex cannot be elicited even by an external stimulus.
Mrs. X is a patient with bipolar affective disorder with secondary amenorrhea. The investigation to be done
is
Select one:
1. Serum testosterone levels
2. FSH and LH levels
3. Thyroid levels
4. Pregnancy test
5. Serum prolactin levels
Pregnancy test
The most common cause of secondary amenorrhoea is pregnancy. Also, anticonvulsants used in bipolar
disorder can reduce the efficacy of oral contraceptives
What percentage of epileptic patients will have normal EEG between attacks?
Select one:
1. 70-90%
2. 1-2%
3. 10-15%
4. 30-50%
5. 5-10%
30-50%
The value of the EEG is that it can suggest an abnormal function in the presence of normal structure. 10-
15% of normal individuals show some abnormality of the EEG. 30-50% of epileptic patients will have normal
EEG between attacks.
Which stages of sleep are considered as slow wave sleep?
Select one:
1. Stage 1 and 2 n-REM sleep
2. Stage 3 and 4 n-REM sleep
3. Stage 0 and 1 n-REM sleep
4. REM sleep
5. Stage 2 and 3 n-REM sleep
Stage 3 and 4 n-REM sleep
REM sleep: The eyes undergo rapid movements, and there is a high level of brain activity. Non-REM sleep:
There is reduced neuronal activity. Stage 3 and 4 of NREM are grouped as slow wave sleep because the
slow delta waves predominate in these two stages.
Flattened trace of EEG is a feature seen in
Select one:
1. Petitmal epilepsy
2. Creutzfeldt Jacob disease
3. Delirium
4. Partial seizures
5. Huntington’s disease
Huntington’s disease
A significant reduction in voltage with a predominant absence of alpha rhythms, sometimes leading to flat
traces, is seen in Huntington’s disease.
The resting membrane potential of a neuron is around
Select one:
1. 170 mv
2. 70 Mv
3. 30 Mv
4. -30 mv
5. -70mV
-70mV
There is a negative resting membrane potential of around 70 mv. It is maintained by the sodium pump,
which actively transports sodium ions out of the cell and potassium ions into the cell. The ATP provides the
energy.
Peak cortisol level in normal physiological states is seen at:
Select one:
1. 10 AM
2. 4 AM
3. 8 AM
4. 6 AM
5. 2 PM
6 AM
A diurnal variation in ACTH and cortisol levels occurs in humans, with peak cortisol levels occurring around
6:00-7:00 AM.
A patient is administered 1g of dexamethasone at 11PM, and his plasma samples are collected to measure hormone levels on the following morning. Which of the following is correct concerning the physiological changes overnight?
Select one:
1. ACTH levels are suppressed
2. CRH levels are increased
3. Glucocorticoid receptors are blocked
4. Prolactin levels are increased
5. Cortisol levels are increased
ACTH levels are suppressed
The dexamethasone suppression test (DST) is used to demonstrate a failure of feedback suppression of
ACTH/CRH and continuous production of endogenous cortisol despite administration of exogenous steroid
(dexamethasone). Normally administering dexamethasone must reduce cortisol in plasma. This is because of intact HPA function leading to reduced ACTH and CRH. In depression and other psychiatric
hypercortisolemic states (also in organic hypercortisolemic states such as Cushing’s), this does not occur.
Which one of the following exists as CNS neurotransmitter as well as a hormone?
Select one:
1. Glucagon
2. Serotonin
3. Vasopressin
4. Dopamine
5. Thyroxine
Vasopressin
Neuropeptides (e.g., endorphins, enkephalins, vasopressin) exist as neurotransmitters and as hormones. By clinging to the nerve cell membrane for varying periods of time, they can modulate the flow of
information. Thus, they are referred to as neuromodulators.
A 47-year-old lady presents with low mood and lethargy. She is noted to have a history of untreated
hypothyroidism. Which of the following is inconsistent with a diagnosis of hypothyroidism?
Select one:
1. Increased TSH levels in blood
2. Cold intolerance
3. Decreased libido
4. Weight gain
5. Tachycardia
Tachycardia
Features of hypothyroidism are: Fatigue, Depressed mood, Weight gain Decreased libido, Cold intolerance,
Psychomotor retardation, Dry skin and Poor memory.
Generalised spike-wave discharges with decreased waves on photic stimulation are seen in EEG of
patients with;
Select one:
1. Myoclonic epilepsy
2. Absence seizures
3. Generalised seizures
4. CJD
5. Angelmann syndrome
Generalised seizures
A decreased wave on photic stimulation followed by generalised spike and wave discharges is seen in
patients with generalised tonic-clonic seizures.
Which one of the following classes of drugs increases beta activity?
Select one:
1. Lithium
2. Anticonvulsants
3. Benzodiazepines
4. Antipsychotics
5. Antidepressants
Benzodiazepines
Antipsychotics and antidepressants produce slowing of beta activity with an increase in theta and delta
activity. Alcohol, Barbiturates and Benzodiazepines increases beta activity, frequently mixed with low amplitude theta activity. Lithium may produce some slowing of the alpha rhythm. Anticonvulsants,
analgesics, beta blockers and narcotics have little effect on the EEG.
Which one of the following ions is freely permeable across cell membranes?
Select one:
1. Chloride ions
2. All of the listed options
3. Sodium ions
4. Potassium ions
5. Organic ions
Chloride ions
Potassium ions-Relatively permeable Sodium ions-relatively impermeable Chloride ions-freely permeable
Organic ions-relatively impermeable
Which of the following receptor on stimulation leads to sleep onset?
Select one:
1. Noradrenergic - receptors
2. 5HT2 receptors
3. Glucocorticoid receptors
4. Histaminergic receptors
5. Cholinergic receptors
Cholinergic
The noradrenergic rapid eye movement (REM)-OFF neurons in locus coeruleus and cholinergic REM-ON
neurons in tegmentum show a reciprocal firing pattern. The REM-ON neurons fire during REM sleep
whereas REM-OFF neurons stop firing during REM sleep.
The delta waves have a frequency of
Select one:
1. 13-40 Hz
2. 8-13 Hz
3. 3.5-7.5 Hz
4. 7-11 Hz
5. Less than 4 Hz
Less than 4 Hz
EEG-Different wave forms are classified by frequency: Alpha-8-13Hz Beta 13-40 Hz Theta 4-8 Hz Deltaless
than 4Hz
At resting membrane potential which ion is greatest in concentration inside the cell?
Select one:
Chloride
Calcium
Sodium
Magnesium
Potassium
Potassium
At resting membrane potential, there are more potassium ions inside and more sodium ions outside the plasma membrane
Regarding major depression, which of the following statements on neuroendocrine abnormalities is correct?
Select one:
1. Large dose of cortisol exacerbates depressive symptoms
2. 50% of patients show raised cortisol levels
3. Low levels of corticotrophin releasing factor is found in CSF of patients
4. Dehydroepinandrosterone levels are low
5. Atrophy of adrenal cortex is seen in 20% of patients
50% of patients show raised cortisol levels
Many depressed patients have a high level of cortisol in plasma and urine. It is now known that 50% of
depressed patients exhibit hypercortisolemia.
Which of the following is associated with low levels of cortisol?
Select one:
1. PTSD
2. Depression
3. Anorexia
4. Psychosis
5. Mania
PTSD
In PTSD hypocortisolemia is seen in a subgroup of patients; this may be due to aberrant feedback to the
pituitary due to excessive glucocorticoid receptors - probably a genetic vulnerability.
EEG changes in Angelman’s syndrome are notable by the age of
Select one:
1. Soon after birth
2. Two years
3. Puberty
4. 7 years
5. 21 years
Two years
In Angelman syndrome, EEG changes are notable by the age of 2. Prolonged runs of high amplitude 2-3 Hz
frontal activity with superimposed interictal epileptiform discharges are seen in all ages More than2. Occipital high amplitude rhythmic 4-6 Hz activity facilitated by eye closure is seen under the age of 12 years. There is no difference in EEG findings in AS patients with or without seizures
There is a nocturnal surge in the level of growth hormones during which of the following stages of sleep?
Select one:
1. After waking up
2. All stages of sleep
3. Stage 1 and 2 n-REM sleep
4. Stage 3 and 4 n-REM sleep
5. REM sleep
Stage 3 and 4 n-REM sleep
The growth hormone regulates carbohydrate and lipid metabolism. There is a nocturnal surge during slow
wave sleep. Its release is inhibited by somatostatin, and it inhibits the peripheral production of the Insulin like growth factor (IGF-1).
Which of the following sleep EEG changes is seen when taking benzodiazepines for insomnia?
Select one:
1. Increased slow wave sleep
2. Reduced stage 1 sleep
3. Reduced stage 2 sleep
4. Increased REM sleep
5. Reduced REM latency
Reduced stage 1 sleep
Multiple sleep-related changes including a decrease in sleep latency, increased sleep time, reduced stage 1
sleep, increased stage 2 sleep, reduced REM and Slow Wave Sleep, and REM rebound on cessation are
seen with benzodiazepines.
Which of the following stages of sleep predominates in a neonate?
Select one:
1. Stage 2 sleep
2. Stage 3 sleep
3. Stage 4 sleep
4. Stage 1 sleep
5. REM sleep
REM sleep
Newborns sleep about 16 hours a day. They spend More than 50% of sleep time in REM sleep. Sleep-onset
REM is also seen in neonates.
Orexin (hypocretin) neurons are dysfunctional in which of the following disorders?
Select one:
1. Obesity
2. Catatonia
3. Chorea
4. Anorexia
5. Narcolepsy
Narcolepsy
The VLPO- ventrolateral preoptic nuclei - induces sleep by putting the brakes on the arousal nuclei. This
switching is stabilised by orexin neurons (also called hypocretin) from the hypothalamus. Patients with
narcolepsy have few orexin neurons in the hypothalamus. Orexin neurons are mainly active during wakefulness and reinforce the arousal system.
The EEG wave with a frequency of 4 to 8 Hz is
Select one:
1. Theta
2. Delta
3. Alpha
4. Gamma
5. Beta
Theta
EEG-Different wave forms are classified by frequency: Alpha: 8-13Hz
Beta: 13-40 Hz
Theta: 4-8 Hz
Delta: less than 4Hz.
Theta and delta are also called slow waves due to their low-frequency band.
The levels of ACTH and CRF is increased and plays an important role in the neuroendocrinology of;
Select one:
1. Autism
2. Dementia
3. Schizophrenia
4. Depression
5. Biploar disorder
Depression
The dexamethasone suppression test (DST) is used to demonstrate a failure of feedback suppression of
ACTH/CRH and continuous production of endogenous cortisol despite administration of exogenous steroid
(dexamethasone). Normally administering dexamethasone must reduce cortisol in plasma. This is because of intact HPA function leading to reduced ACTH and CRH. In depression and other psychiatric
hypercortisolemic states (also in organic hypercortisolemic states such as Cushing’s), this does not occur, and ACTH/CRF levels are raised.
Regular 3 Hz complexes are seen in EEG of patients with which of the following conditions?
Select one:
1. ADHD
2. CJD
3. Antisocial personality disorder
4. Angleman’s syndrome
5. Absence seizures
Absence seizures
Regular 3 Hz complexes are commonly seen in EEG of patients with Absence seizures (Petit-mal type of
epilepsy)
Which of the following physiological changes are noted after ECT in clinically depressed individuals?
Select one:
1. Reduced noradrenaline turnover
2. Beta waves predominance in EEG
3. Reduced ß receptors
4. Increased a2 receptors
5. Increase in 5HT2 receptors
Reduced ß receptors
After ECT treatment, EEG immediately shows delta and theta excess but returns to normal levels after
three months of the end of treatment. Reduced ß noradrenergic receptor and increased noradrenaline
turnover is also noted. Alpha 2 receptors are reduced in a change that is similar to antidepressants. Brain 5-
HT2 receptors were considered potential targets for therapeutic efficacy of electroconvulsive therapy (ECT),
but pre-clinical studies showed that electroconvulsive shock up-regulates 5-HT2 receptors in contrast to
antidepressant medications, which down-regulate brain 5-HT2 receptors. Using an [18F]setoperone PET
scan Yatham and Liddle (2010) have now demonstrated that unlike in rodents, and similar to
antidepressants, ECT reduces brain 5-HT2 receptors in individuals with depression.
The frequency of ß waves seen in normal EEG is
Select one:
1. 8-13 Hz
2. More than 40Hz
3. 4-8Hz
4. Less than 7 Hz
5. More than 13Hz
More than 13Hz
EEG-Different wave forms are classified by frequency: Alpha: 8-13Hz
Beta: 13-40 Hz
Theta: 4-8 Hz
Delta: less than 4Hz
Infants have a dominant rhythm in which of the following EEG wave frequency?
Select one:
1. 3 Hz
2. 10 Hz
3. 13 Hz
4. 40 Hz
5. 7 Hz
3 Hz
The infants have a dominant rhythm of 3 Hz, the dominant frequency increases with maturation. In the
newborn, the EEG is dominated by delta and theta waves.
A 42-year-old man is a journalist. He goes to sleep at 10PM every night and wakes up at 5:30AM every
morning. If he volunteers for a sleep study using polysomnogram the time from sleep onset to first REM
episode will be
Select one:
1. 30 minutes
2. 60 minutes
3. 160 minutes
4. 10 minutes
5. 90 minutes
90 minutes
REM latency: Time from sleep onset to first REM episode. Normally it is about 90 minutes in adults.
Mr. Y presents to the emergency department with a history of apathy and weight loss. On further
investigations, he has hyponatraemia and hyperkalemia. What is his possible diagnosis?
Select one:
1. Acute porphyria
2. Cushing’s syndrome
3. Cohn’s syndrome
4. Diabetes insipidus
5. Addison’s disease
Addison’s disease
The most common symptoms of Addison’s disease are fatigue, lightheadedness, muscle weakness, apathy,
fever, weight loss, anxiety, nausea, vomiting, diarrhea, headache, sweating, changes in mood and
personality, joint and muscle pains. Some have marked cravings for salt or salty foods due to
hyponatraemia. Affected individuals may note increased tanning since adrenal insufficiency is manifested in the skin primarily by hyperpigmentation.
Other features include hypoglycemia, low blood pressure, hyperkalemia and hypercalcemia
The duration of normal sleep latency in healthy adults is
Select one:
1. 15-20 minutes
2. 30-40 minutes
3. 0-5 minutes
4. 90-100 minutes
5. 50-60 minutes
15 -20 minutes
Sleep latency is the time from lights out to sleep onset. A sleep onset latency of 15 to 20 minutes is
indicative of “little or no” sleep debt. REM latency: Time from sleep onset to first REM episode. Normally it
is about 90 minutes in adults.
A 3 months old newborn undergoes awake EEG investigation to detect seizure activity, but no abnormalities were found. Which of the following waveform will be prominent in the recording?
Select one:
1. Delta and theta
2. Spindle waves
3. Alpha and beta
4. Mu and lambda
5. K complexes
Delta and theta
Newborns have dominant delta and theta waves. Infants have irregular medium- to high-voltage delta
activity in the awake tracing of the infant; alpha range develops in posterior areas by early childhood; by
mid-adolescence EEG essentially has the appearance of an adult tracing. The normal dominant alpha
rhythm is usually achieved by 12-14 years old
Peak cortisol level in normal individuals is noted around
Select one:
1. 12 AM Mid night
2. 9 AM after breakfast
3. 6 AM in the morning
4. 12 PM Mid day
5. 6 PM in the evening
6 AM in the morning
A diurnal variation in ACTH and cortisol levels occurs in humans, with peak cortisol levels occurring around
6:00-7:00 AM.
